[GRASS-dev] get_row.c: output north/east values? G__.window structure

[Dylan Beaudette]

On Tuesday 26 August 2008, Markus Neteler wrote:
> On Tue, Aug 26, 2008 at 3:10 PM, Glynn Clements
>
> <glynn at gclements.plus.com> wrote:
> > Markus Neteler wrote:
> >> I try to understand an issue mentioned on grass-user but get only
> >> enigmatic error messages:
> >>
> >> v.extrude -t bldg_cmcl  out=bldg_cmcl_3d height=15
> >> elev=el_D792_6m --o
> >> WARNING: Vector map <bldg_cmcl_3d> already exists and will be
> >> overwritten
> >>
> >> WARNING: Reading raster map <el_D792_6m at PERMANENT> request for row
> >> 220803 is outside region
> >> ERROR: Problem reading raster map
>
> ...
>
> > Any warning generated there is useless to the end user, as it
> > indicates a bug in the code. It's the caller's responsibility to avoid
> > requesting rows which lie outside the current region.
> >
> >
> > I've committed fixes to a number of bugs in G_get_raster_sample().
> > Apart from trying to read invalid rows, it was deliberately reading
> > the wrong rows at the edge of the region, and pretending that nulls
> > were zero (they aren't; just because you would like a definite (i.e.
> > non-null) answer, that doesn't mean that you can have one).
>
> I have backported this.
>
> > I've also fixed v.sample to deal with the fact that the result may be
> > null.
> > v.extrude and v.drape also use that function, so they may need similar
> > changes.


Not able to comment on the patch, but I can confirm that v.drape uses 
G_get_raster_sample()  in  GRASS64. v.drape tests for vector input features 
lying outside of the current region / extent of the input raster... However I 
don't think that it is currently done in a very robust way. Also, if the 
input vector is not contained within the input raster / current region a 
warning is raised and a 0 is written to the z coordinate. Perhaps a different 
behavior would be more robust.

Ideas?

Cheers,

Dylan


-- 
Dylan Beaudette
Soil Resource Laboratory
http://casoilresource.lawr.ucdavis.edu/
University of California at Davis
530.754.7341